i don't know, a 30 liter tank is a bit small for two dwarfs. the males can be very territorial. even if you found a female to go with your male, there isn't much room in there, especially with the other fish. its not big enough to allow the males to hide from one another/avoid each other. you'd need a bigger tank and tons of plants/places to hide. you could try it, you might just luck out and find yourself with two passive males, but i wouldn't recommend it, especially with the other tank mates...................